The present invention relates to water filtration. More particularly, the invention relates to a reverse osmosis water filtration system wherein gentle periodic back pressure across the filter membrane is utilized to avoid the aggregation of microbial bioburden within the filtration system.
The need to control microbial bioburden has led to point-of-use bacterial sterilization using filter membranes to remove particles and bacteria from various fluids. It is important, however, that the utilized filter membranes be regularly maintained in order to prevent the buildup of microbial biological fouling on the upstream side of the filter membrane. In reverse osmosis filter technology, such regular maintenance generally entails the replacement of the reverse osmosis filter membrane and/or the entire reverse osmosis filter assembly. Unfortunately, depending upon the remoteness of the filter implementation or the skill level of the user, the filter assembly may be neglected, ultimately resulting in failure or even health hazard.
Because microbial bioburden is most prevalent in stagnant water, Applicant has found it desirable to implement extra precaution against the biological fouling of reverse osmosis filter membranes. To this end, it is an object of the present invention to provide a reverse osmosis filter system wherein there is provided a continuous flow of water across the filter membrane. Contrary to the general state of the art, this requires the back flow of filtered water across the filter membrane. Although U.S. Pat. No. 5,658,457 issued Aug. 19, 1997 to Schoenmeyr (xe2x80x9cSchoenmeyrxe2x80x9d) at least contemplates such a back flow for the purpose of particle removal, Schoenmeyr falls short of enabling a system capable of resisting microbial buildup. In particular, Schoenmeyr fails to provide sufficient back flow pressure at the time of forward flow shut-off as necessary for actual reverse flow across the membrane. As a result, the apparatus of Schoenmeyr is susceptible to the buildup of biological material. It is therefore an overriding object of the present invention to improve upon the prior art by providing a reverse osmosis filter system that provides for the continuous flow of water across the reverse osmosis membrane, thereby greatly diminishing the opportunity for the aggregation of biological fouling.
In accordance with the foregoing objects, the present inventionxe2x80x94a microbial resistant water purification and collection systemxe2x80x94generally comprises a reverse osmosis filter assembly having a filter inlet in selective fluid communication with a system inlet and a filter outlet in fluid communication with a water storage container. The filter inlet is separated from the filter outlet by a filter membrane. At least a portion of the storage container is located at an elevation above the filter membrane such that filling of the storage container creates a head pressure in the storage container relative to the filter membrane.
A shut-off valve is interposed the system inlet and the filter inlet to block fluid communication from the system inlet to the filter inlet upon reaching a minimum head pressure in the storage container relative to the filter membrane. In the preferred embodiment of the present invention, the minimum head pressure is at least 0.5 pounds per square inch in order to ensure back flow across the membrane upon shut-off to the filter assembly of the source water.
The water storage container preferably comprises a substantially freely expandable and substantially freely collapsible, flexible bag while the shut-off valve preferably comprises a mechanical valve, actuated by the filling of the flexible bag. In particular, the mechanical valve comprises a valve inlet, a valve outlet and a plunger, depression of the plunger operating to block fluid flow from the valve inlet to the valve outlet. To this end, the shut-off valve further comprises a lever arranged between the mechanical valve and the flexible bag such that the lever is adapted to depress the plunger upon substantial filling of the flexible bag.
In at least one embodiment of the present invention, the reverse osmosis filter assembly is located in a space entirely beneath the storage container, thereby providing maximum head pressure to the filter membrane. In this embodiment, the filter outlet communicates with the storage container through a container inlet in a base portion of the storage container. The same inlet may also then double as an outlet for the water collected in the storage container. To this end, a transfer pump, which may be demand activated, gas powered, remotely switched or a combination thereof, may also be provided for delivery of the water.
A booster pump may be interposed the system inlet and the filter inlet for low source pressure applications. In this case, a shut-off switch adapted to interrupt electrical power to the booster pump upon substantial filling of the storage container is also provided. Preferably, the shut-off switch is actuated by the same lever as controls flow to the filter assembly. Additionally, a clean water inlet for collection of water other than through the filter assembly may be provided. In this case, a pressure relief, having an integral check valve, is provided for release from the collected water of gasses such as carbon dioxide.
Finally, many other features, objects and advantages of the present invention will be apparent to those of ordinary skill in the relevant arts, especially in light of the foregoing discussions and the following drawings, exemplary detailed description and appended claims.